New Stanford-developed method finds tumors in children without exposing them to radiation

UPDATE: This entry has been corrected from a previous version, which incorrectly implied that these scans were used for cancer screening.

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Sometimes, getting a clear picture of the tumors in a newly-diagnosed cancer patient requires exposing the patient to potentially harmful ionizing radiation, which can be particularly harmful to young patients who are still growing. Now, researchers from Lucile Packard Children’s Hospital Stanford have developed a technique to scan for tumors that takes radiation out of the equation, lowering the young patients’ risk of later developing secondary tumors.

The new method… is a modification of magnetic resonance imaging that employs a novel contrast agent to find tumors. The MRI-based method is as effective as cancer-detection scans that use ionizing radiation — specifically, positron emission tomography-computed tomography — the researchers found.

Although whole-body PET-CT technology provides essential information for detecting cancer, it has one big drawback: A single scan exposes the patient to as much radiation as 700 chest X-rays.

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To find tumors via MRI, the Stanford team used a new contrast agent consisting of nanoparticles of iron. Injections of these iron nanoparticles are approved by the Food and Drug Administration to treat anemia, and the researchers obtained FDA permission for the experimental use. The nanoparticles are retained in the body for many days. On MRIs, they cause blood vessels to appear brighter, providing anatomic landmarks. The nanoparticles also cause healthy bone marrow, lymph nodes, liver and spleen to appear darker, making tumors stand out.

The images generated from the experimental MRIs provided comparable information to the PET-CT scans that study subjects received as part of their care. The PET-CTs detected 163 of 174 total tumors in the 22 patients; the MRIs found 158 of 174 tumors. The two methods had similar levels of sensitivity, specificity and diagnostic accuracy.

The method is described in a paper published today in The Lancet Oncology. “I’m excited about having an imaging test for cancer patients that requires zero radiation exposure,” senior author Heike Daldrup-Link, MD, associate professor of radiology at Stanford and a diagnostic radiologist at the hospital, told my colleague. “That is a big deal.”